Carl Von Ahrens was born on February 15, 1862 in Winfield, Ontario. His parents soon separated and Ahrens was raised by his father in Kitchener. He contracted tuberculosis at around age five. The disease settled in his hip instead of his lungs, reportedly due to an injury to the joint. Several family members, including his father, died of the disease. Ahrens was known all over Waterloo County as a prankster.
He worked many random jobs before commiting his life to art. In 1878 Ahrens's family sent him to Winnipeg to work in a law firm. He quickly dismissed this profession, and after two adventurous years his family demanded he come home to Ontario. He worked in a button factory, the tedious and delicate process of dyeing buttons intrigued him and he later considered this job his first step toward the mastery of color, a skill that distinguished him as a painter. Following his work at the button factory, Ahrens was sent to Stratford to apprentice as a dentist under his uncle, Alfred Ahrens. Ahrens swiftly mastered everything that Dr. Ahrens could teach. He could not practice in Ontario without a degree, so he moved to Nebraska City, Nebraska, to open a practice of his own, which was a great success. On an extended trip home to Ontario, Ahrens met and married Emily Marion Carroll, they had a son Carl Herman.
Ahrens began to paint in 1886, at the age of 24 and within a year he gave up dentistry, a profession he had never enjoyed. When the Ahrens family heard of his decision, they turned their backs on him, hoping poverty would make him see the error of his ways. Determined to succeed he moved his family to Toronto and began work in a studio on Adelaide Street. By age of 27 he was known as an up-and-coming artist, and his vast social circle included painters, journalists and actors. He was particularly close with the Mohawk recitalist and poet, Pauline Johnson. Ahrens had little formal instruction in painting. He worked alone, watching the methods of other painters but never feeling compelled to copy them. His first exhibition was with the Ontario Society of Artists in 1889. In 1891 he was elected Associate Painter in the Royal Canadian Academy of Arts.
He eventually went to New York City to study painting under William Merritt Chase and sculpture under Francis Edwin Elwell. While there he befriended painter, George Inness, who became his mentor. Inness encouraged Carl to stop taking classes, go home and paint how he wished to paint. Ahrens took his advice, returned to Toronto, resigned from all professional associations and, while initially famous for his portraits, he turned almost exclusively to landscapes. He moved to New York temporarily, and returned to Toronto in the summer of 1907, settling in the village of Meadowvale.
Ahrens last years were unfortunately very unpleasant as he fell very ill. He continued to paint and his last works are full of vibrant color. Old friend, Prime Minister William Lyon Mackenzie King arranged for Ahrens to be taken care of for the last months of his life in the Toronto Psychiatric Hospital. He died on February 27th, 1936 at the age of 74.